Putting a human face on global warming, “Beautiful Islands” is a handsome-looking, if narratively inert, piece of propaganda filmmaking.

This Japanese documentary joins images, unaccompanied by narration or music, from three island communities beset by flooding and whose coastlines are threatened — the Pacific archipelago of Tuvalu (whose future has earned it the predictive billing of “first nation to sink”), Venice and a village in western Alaska.

To say the least, the film doesn’t tell the whole story. Venice has been sinking since the day the first pigeon touched down in Piazza San Marco, and global warming means some land lost to the seas but also some previously frosty land opened up for farming. And “Beautiful Islands” isn’t a powerhouse of storytelling, lingering at extended, boring length to observe traditional dance ceremonies or children playing in the water.

But there are compelling moments, such as the scenes of Venetians dealing casually with ankle-high waters in their hotel lobbies and restaurants. And though the tactic of (in this case tacitly) urging policy change by anecdote is intellectually insipid (since a story or three from the opposite point of view could easily be assembled), it can work on an emotional level.